JPH06221565A - Thermal cooker - Google Patents

Abstract

PURPOSE:To provide a thermal cooker which enables the detection of a trouble of a hot-air circulation fan. CONSTITUTION:A heater 8 for an oven is provided behind a heating chamber 5 and a hot air circulation fan 6 is provided near the heater 8 for an oven to circulate hot air heated with the heater 8 for an oven through the heating chamber. A temperature detector 9 for an oven is provided to detect the temperature near the hot air circulation fan 6, an internal chamber temperature detector 17 to detect an internal temperature of the heating chamber 5 and an abnormality detecting section to output an abnormality signal when an output difference between a temperature signal outputted from the internal chamber temperature detector 17 and the temperature signal outputted from the temperature detector 9 for an oven is larger than a threshold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating cooker such as a microwave oven, and more particularly to detecting an abnormality in the heating cooker.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
There is one shown in. The microwave oven 50 includes a convection unit 52 behind the heating chamber 51, and a turntable 53 for placing and rotating the object 100 to be heated on the bottom of the heating chamber 51. The convection unit 52 includes a hot air circulation fan 54 and a convection motor 5 that rotationally drives the hot air circulation fan 54.
5, an oven heater 56 arranged around the hot air circulation fan 54, and an oven thermistor 57 for measuring the temperature in the vicinity of the oven heater 56. The hot air circulation fan 54, the oven heater 56, and the oven thermistor 57 are housed in a convection duct 58 formed in communication with the rear surface of the heating chamber 51. The convection duct 58 is covered with a heat insulating material 59, and a self-cooling fan 60 connected to the rotation shaft of the convection motor 55 is provided outside the convection duct 58.
Is provided. The microwave oven 50 is provided with a high frequency generating circuit for high frequency cooking, which is not shown.

When the oven is heated in the microwave oven 50, power is supplied to the oven heater 56 to generate heat and the convection motor 55 is rotated. Then, the hot air circulation fan 54 sucks the air in the heating chamber 51 from the air inlet 61 at the center of the rear surface of the heating chamber 51 and blows it onto the oven heater 56. The blown air removes heat from the heater 56 for the oven, and then becomes hot air from the blower opening 62 on the outer rear surface of the heating chamber 51 to the heating chamber 51.
It is blown out inside. The hot air blown out circulates in the heating chamber 51, and then is sucked into the convection duct 58 again from the intake port 61. In this way, hot air is circulated in the heating chamber 51. At this time, the temperature of the hot air is measured by the oven thermistor 57, and the heating chamber 5 is controlled by controlling the energization of the oven heater 56 based on the measured value.
The object to be heated 100 is baked while the room temperature of No. 1 is kept constant.

On the other hand, the self-cooling fan 60 is rotated by the rotation of the convection motor 55, and while the convection motor 55 is cooled by the outside air sucked from the center of the self-cooling fan 60, the oven heater is blown out of the self-cooling fan 60. The structure is such that the heat insulating material 59 heated by the heat of 56 is efficiently cooled.

[0005]

By the way, in the above-mentioned oven 50, the hot air circulation fan 54, the self-cooling fan 60, and the deformation of the oven range side wall portion around these fans 54, 60, etc.
The hot air circulation fan 54 may be unable to rotate when 4, 60 is constrained by the side wall of the microwave oven, or when the convection motor 55 itself has an electrical abnormality.

In such a case, since the hot air circulation fan 54 does not circulate the hot air between the heating chamber 51 and the convection duct 58, the outer temperature of the microwave oven 50 becomes abnormally high. The temperature of the oven heater 56 itself rises, the coil is broken, the radiant heat from the oven heater 56 becomes hot, the convection duct 58 is damaged, and the uneven heating of the object 100 to be heated occurs. Since the cooling is not performed by the self-cooling fan 60, the convection motor 55 may be burned, which may cause an inconvenience.

Therefore, an object of the present invention is to provide a heating cooker capable of detecting a failure of the hot air circulating fan which causes such an inconvenience.

[0008]

In order to achieve such an object, according to the present invention, an oven heater provided at the rear of the heating chamber and an oven heater provided near the oven heater are provided. In a heating cooker equipped with a hot air circulation fan for circulating hot air heated in the heating chamber and a temperature detecting element for an oven for detecting the temperature in the vicinity of the hot air circulation fan, a chamber for detecting the indoor temperature of the heating chamber An abnormality detection device that includes a temperature detection element and outputs an abnormality signal when the output difference between the temperature signal output by the indoor temperature detection element and the temperature signal output by the oven temperature detection element is larger than a threshold value. A heating cooker was configured with parts.

[0009]

According to the above construction, when the hot air circulating fan becomes unrotatable due to a failure, hot air circulation does not occur in the heating chamber, so the temperature rising speed in the vicinity of the hot air circulating fan is faster than in normal operation. The temperature rise in the heating chamber becomes slow.

Therefore, the temperature rise amount in the vicinity of the hot air circulation fan is detected by the oven temperature detection element, the temperature rise amount in the heating chamber is detected by the indoor temperature detection element, and the output difference is preset in the abnormality detection unit. Compare with threshold value. If the output difference is larger than the threshold value, the temperature rising speed in the vicinity of the hot air circulation fan is abnormally high, that is, it is considered that the hot air circulation fan has failed, and an abnormal signal is output. To do.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a side sectional view of an oven of a grill microwave oven, which is a heating cooker according to the present invention, when heating the oven, and FIG. 2 is a front sectional view of the grill when heating the grill.
Is a circuit diagram thereof, FIG. 4 is a flow chart of failure detection of the hot air circulating fan during heating of the oven, FIG. 5 is a diagram showing changes in output signals of the thermistor for the oven and the thermistor for grill when the hot air circulating fan is normal, and FIG. It is a figure which shows the change of the output signal of the thermistor for ovens and the thermistor for grills at the time of a hot-air circulation fan failure.

The grill microwave oven 1 comprises a convection unit 2, a grill portion 3, and a turntable 4. The convection unit 2 is disposed behind the heating chamber 5, the hot air circulation fan 6, the convection motor 7 that drives the hot air circulation fan 6 to rotate, and the oven heater 8 disposed around the hot air circulation fan 6.
And an oven thermistor 9 that measures the temperature in the vicinity of the oven heater 8. The hot air circulation fan 6, the oven heater 8, and the oven thermistor 9 are connected to the rear surface of the heating chamber 5 to form a convection duct 1.
It is stored in 0. The convection duct 10 is covered with a heat insulating material 11, and a self-cooling fan 12 fixed to the rotation shaft of the convection motor 7 is provided outside the convection duct 10. The grill part 3 is provided with a heater 13 for the grill provided on the top surface of the heating chamber 5.
And a reflector 14 provided to cover the grill heater 13.
In addition, the grill thermistor 17 is provided on the side surface of the heating chamber 5 below the shelf receiver 36 for positioning the grill tray 37. In the present embodiment, the grill thermistor 17 also serves as an indoor thermistor. The turntable 4 is provided at the bottom of the heating chamber 5, and the object 100 to be heated is placed and rotated.

Further, as shown in the circuit diagram of FIG. 4, the grill microwave oven 1 has a control circuit 20 for controlling the entire cooking.
Is equipped with. In this embodiment, the control circuit 20 includes an abnormality detecting section and a second abnormality detecting section. And
Based on the control signal from the control circuit 20, the convection motor 7, the oven heater 8, and the grill heater 1
A CM relay 21, an oven relay 22, and a grill relay 23 for controlling the supply of driving power to the No. 3 are provided. The grill microwave oven 1 is also capable of high frequency cooking, and in FIG.
Reference numeral 5 is a high frequency generation circuit relay. Further, 26 is an interior light lamp, 27 is an interior light relay, 28 is a turntable motor, 29 is a turntable relay, 30 is an interface, 31 is an A / D conversion circuit, and 32 is an input section for various cooking settings. .

When performing oven heating, the control circuit 20 controls the oven relay 22 and the CM relay 21 to supply power to the oven heater 8 to generate heat and rotate the convection motor 7. Then, the hot air circulation fan 6 rotates to suck the air in the heating chamber 5 from the intake port 33 at the center of the rear surface of the heating chamber 5 and blow it on the heater 8 for the oven to remove the heat of the heater 8 for the oven.
The heated hot air is blown into the heating chamber 5 from the blower port 34 on the rear surface of the heating chamber 5 to circulate the hot air and burn the object 100 to be heated. At that time, the temperature of the hot air is detected by the thermistor 9 for the oven, and the control circuit 20 opens and closes the oven relay 22 based on the detection result to control the heater 8 for the oven to keep the indoor temperature constant. ing.

On the other hand, the rotation of the convection motor 7 also rotates the self-cooling fan 12, and the rotation of the self-cooling fan 12 cools the convection motor 7 with the outside air sucked from the center of the self-cooling fan 12 and also the self-cooling fan 12 is rotated. The heat blown to the outside efficiently cools the heat insulating material 11 warmed by the heat of the heater 8 for the oven.

Next, the failure detection operation of the hot air circulation fan 6 during heating of the oven will be described with reference to the flowchart of FIG. This failure detection operation is performed by paying attention to the following difference in heating temperature change between the case where the hot air circulation fan 6 is operating normally and the case where it fails. That is, when the hot air circulation fan 6 is operating normally, as shown in FIG. 5, the temperature in the heating chamber 5 rises along with the temperature in the vicinity of the oven heater 8, and the temperature of the grill thermistor 17, which is an indoor thermistor, increases. The maximum I is between the output signal G _TH and the output signal O _TH of the oven thermistor 9.
There is only a slight output difference.

On the other hand, when the hot air circulation fan 6 fails and cannot rotate, the temperature in the vicinity of the heater 8 for the oven rises abnormally, while the temperature in the heating chamber 5 rises, as shown in FIG. It does not rise so much, and therefore, the maximum value of H between the output signal G _{TH of the} thermistor 17 for grill and the output signal O _TH of the thermistor 9 for oven is larger than that during normal operation.
There is some output difference. Therefore, the present invention detects a failure of the hot air circulation fan 6 by determining such a difference in output difference.

Specifically, this detecting operation is composed of a first flow and a second flow. In the first flow, first,
The oven heating is started and the oven relay 22 and the CM relay 21 are turned on (S1 to S3). Then, the output signal O _{TH of} the thermistor 9 for the oven and the thermistor 17 for the grill in the oven heating state by the control circuit 20,
G _TH is read and the output difference A is calculated (S4 to S
6). On the other hand, the control circuit 20 previously stores an arbitrary threshold value B. The threshold value B is determined as an arbitrary value (H>B> I) between the maximum output difference I during normal operation and the maximum output difference H during failure as described above. Then, the output difference A is compared with the threshold value B,
If A ≦ B, it is determined that the operation is normal, and the driving of the oven heater 8 and the hot air circulation fan 6 is continued.
Then, if A> B, it is determined that there is a high possibility that the hot air circulation fan 6 has a failure, and an abnormal signal is output, and the process proceeds to the second flow (S7).

In the second flow, upon receipt of the abnormal signal, the output signal O _TH of the thermistor 9 for the oven is read again and stored in the control circuit 20 as the initial storage value D (S).
8, S9). Then, the CM relay 21 is turned off to temporarily stop the energization of the convection motor 7. It is appropriate that the pause time is about 5 to 10 seconds (S10, S1
1). After the energization is temporarily stopped, the output signal O _TH of the thermistor 9 for the oven is read again and stored as the final storage value E in the control circuit 20 (S12, S13). Then, the final memory value E is compared with the initial memory value D (S1).
4).

Here, when the hot air circulating fan 6 really fails and cannot rotate, the hot air circulating fan 6 remains unrotatable regardless of whether or not the convection motor 7 is energized. The non-blowing state to the heating chamber 5 does not change at all, and therefore the output signal of the oven thermistor 9 does not change before and after the operation of the CM relay 21. Therefore, if D = E, the failure of the hot air circulation fan 6 is considered to be true, and the oven relay 22 is turned off to stop the oven heating (S15).

On the other hand, if the first detection flow is erroneously passed through due to noise or the like, the drive of the convection motor 7 is stopped and the hot air circulation is stopped for the first time by the temporary stop, so the initial stored value D and the final stored value E are set. The output signal changes with and. Therefore, if D ≠ E,
It is considered that the erroneous determination is made in the first flow, the CM relay 21 is turned on again, and the heating is continued by returning to the first flow (S16).

Next, the operation of heating the grill in the grill microwave oven 1 will be described.

At the time of heating the grill, the object 100 to be heated is placed on the net stand 35 and then placed on the grill tray 37 positioned by the shelf receiver 36. In this state, the control circuit 20 turns on the grill relay 23 to supply power to the grill heater 13 to cause the grill heater 13 to generate heat, and the object 100 to be heated is heated by the heat rays emitted from the grill heater 13. Since the temperature of the grill tray 37 also rises as the object to be heated 100 is heated, the rate of temperature rise and the temperature are determined by the grill thermistor 17.
Of the output signal G _TH , and the heating state thereof is judged by the control circuit 20.

As described above, according to the present invention, it is necessary to provide two thermistors, the thermistor for the oven and the thermistor for the room, in order to detect the failure of the hot air circulation fan 6. However, the grill oven range 1 of the present embodiment is required.
Then, since the grill thermistor 17 which is an existing thermistor and the indoor thermistor are also used for the grill microwave oven, the number of thermistors to be attached does not increase and the manufacturing cost does not rise.

In the case of the microwave oven without the grill thermistor 17, it goes without saying that the same effect can be obtained by providing the heating chamber 5 with a thermistor dedicated to detecting the indoor temperature.

Further, in the above embodiment, the first and second flows are provided in order to detect the failure of the hot air circulating fan 6 with accuracy, but the failure of the hot air circulating flow 6 is detected by either one of the flows. It is also possible to detect.

[0028]

As described above, according to the first aspect of the present invention, it becomes possible to detect the failure of the hot air circulation fan, so that the inconvenience such as the damage due to the abnormal temperature rise can be prevented. Is now possible.

Further, according to the second aspect of the present invention, it is possible to realize an accurate hot air circulating fan failure detection system without malfunction by performing two different failure determinations successively.

Further, according to the third invention, in the microwave oven having the grill heating section, the indoor temperature detecting element can be used also as the grill temperature detecting element. The effect is that it can be done without increasing the cost.

[Brief description of drawings]

FIG. 1 is a side sectional view of a grill microwave oven according to an embodiment of the present invention during heating in an oven.

FIG. 2 is a front cross-sectional view of the grill microwave oven of the embodiment when the grill is heated.

FIG. 3 is a circuit diagram of the grill microwave oven of the embodiment.

FIG. 4 is a flowchart showing each operation of detecting a failure of the hot air circulation fan when heating the oven according to the embodiment.

FIG. 5 is a diagram showing changes in output signals of the oven thermistor and the grill thermistor when the hot air circulation fan is normal in the embodiment.

FIG. 6 is a diagram showing changes in output signals of an oven thermistor and a grill thermistor when a hot air circulation fan fails in the embodiment.

FIG. 7 is a side cross-sectional view of a conventional microwave oven during heating in an oven.

[Explanation of symbols]

 5 Heating Chamber 6 Hot Air Circulation Fan 8 Oven Heater 9 Oven Thermistor 17 Grill Thermistor 20 Control Circuit

Claims (3)

[Claims] 1. An oven heater provided in the rear of the heating chamber, a hot air circulation fan provided near the oven heater and circulating hot air heated by the oven heater in the heating chamber, and a neighborhood of the hot air circulation fan. In a heating cooker having a temperature detecting element for an oven that detects the temperature of the oven, an indoor temperature detecting element that detects an indoor temperature of the heating chamber is provided, and a temperature signal output by the indoor temperature detecting element and the oven A cooker characterized by comprising an abnormality detection unit that outputs an abnormality signal when the output difference from the temperature signal output by the temperature detection element is larger than a threshold value. 2. When the abnormal signal is output, energization of the hot air circulation fan is stopped for a certain period of time, and
A second abnormality detection unit is provided, which compares the output values of the oven temperature detection element before and after stopping the energization, and stops the power supply to the oven heater if there is no change between these output values. Item 2. A heating cooker according to item 1. 3. A grill heater and a grill temperature element for detecting an indoor temperature during cooking of the grill are provided in the heating chamber, and the grill temperature detecting element also serves as the indoor temperature detecting element. The heating cooker according to claim 1 or 2.